CVE-2025-7699 is a high-severity improper authentication vulnerability (CWE-287) found in the EZ Sync Manager component of ASUSTOR's ADM (ASUSTOR Data Master) operating system, specifically affecting versions from 4.1.0 through 4.3.3.RH61 and 5.0.0.RIN1 and earlier. The vulnerability arises due to insufficient authorization checks on the 'file' parameter within HTTP requests handled by the EZ Sync Manager. Authenticated users with legitimate access to the system can exploit this flaw to copy arbitrary files from the server's file system into their own EZ Sync folder. This unauthorized file access is contingent on the target files having readable permissions for other users on the underlying operating system, meaning that while the attacker must be authenticated, they can bypass intended access controls to retrieve sensitive data outside their authorized scope. The vulnerability does not require user interaction or elevated privileges beyond authentication, and it can be exploited remotely over the network (AV:N). The CVSS 4.0 base score is 7.1, reflecting a high severity due to the ease of exploitation (AC:L - low attack complexity), no need for authentication beyond normal user access (PR:L), and the significant confidentiality impact (VC:H) without affecting integrity or availability. No known exploits are currently reported in the wild, and no patches are linked yet, indicating that organizations using affected ADM versions remain at risk until remediation is applied.

For European organizations, this vulnerability poses a significant risk to the confidentiality of sensitive data stored on ASUSTOR NAS devices running the affected ADM versions. Many enterprises, SMBs, and public sector entities in Europe rely on NAS solutions like ASUSTOR ADM for file storage, backup, and synchronization. Exploitation could lead to unauthorized disclosure of intellectual property, personal data protected under GDPR, financial records, or other confidential information. Since the vulnerability allows authenticated users to access files beyond their permission scope, insider threats or compromised user accounts could be leveraged by attackers to escalate data exposure. This could result in regulatory penalties, reputational damage, and operational disruptions. The lack of impact on integrity and availability reduces the risk of data tampering or service outages but does not diminish the severity of data leakage. The vulnerability's remote exploitability and absence of user interaction requirements increase the likelihood of exploitation in environments where user credentials are compromised or insufficiently managed.

European organizations should prioritize the following specific mitigation steps: 1) Immediately audit all ASUSTOR ADM devices to identify versions 4.1.0 through 4.3.3.RH61 and 5.0.0.RIN1 or earlier in use. 2) Restrict user permissions on the underlying OS to minimize readable access to sensitive files, ensuring that only necessary files have read permissions for non-privileged users. 3) Implement strict access controls and monitoring on EZ Sync Manager usage to detect anomalous file access patterns indicative of exploitation attempts. 4) Enforce strong authentication mechanisms, including multi-factor authentication (MFA), to reduce the risk of compromised user credentials being used to exploit this vulnerability. 5) Network segmentation and firewall rules should limit access to ADM management interfaces and EZ Sync Manager endpoints to trusted internal networks or VPNs. 6) Monitor vendor communications closely for official patches or updates addressing CVE-2025-7699 and apply them promptly upon release. 7) Conduct regular security awareness training to alert users about the risks of credential compromise and the importance of secure password practices. These targeted actions go beyond generic advice by focusing on permission hardening, access monitoring, and proactive credential security tailored to the nature of this vulnerability.